<A, E = never, R = never>(
f: (
queue: Queue.Queue<A, E | Cause.Done>
) => Effect.Effect<unknown, E, R | Scope.Scope>,
options?: {
readonly bufferSize?: number | undefined
readonly strategy?: "sliding" | "dropping" | "suspend" | undefined
}
): Stream<A, E, Exclude<R, Scope.Scope>>Creates a stream from a callback that can emit values into a queue.
When to use
Use when you need callback-based code to emit stream values by offering to a
Queue, or signal stream completion through the Queue module APIs.
By default it uses an "unbounded" buffer size.
You can customize the buffer size and strategy by passing an object as the
second argument with the bufferSize and strategy fields.
Example (Creating a stream from a callback that can emit values into a queue)
import { Console, Effect, Queue, Stream } from "effect"
const stream = Stream.callback<number>((queue) =>
Effect.sync(() => {
// Emit values to the stream
Queue.offerUnsafe(queue, 1)
Queue.offerUnsafe(queue, 2)
Queue.offerUnsafe(queue, 3)
// Signal completion
Queue.endUnsafe(queue)
})
)
const program = Effect.gen(function*() {
const values = yield* stream.pipe(Stream.runCollect)
yield* Console.log(values)
// [ 1, 2, 3 ]
})
Effect.runPromise(program)export const const callback: <A, E = never, R = never>(
f: (
queue: Queue.Queue<A, E | Cause.Done>
) => Effect.Effect<unknown, E, R | Scope.Scope>,
options?: {
readonly bufferSize?: number | undefined
readonly strategy?:
| "sliding"
| "dropping"
| "suspend"
| undefined
}
) => Stream<A, E, Exclude<R, Scope.Scope>>
Creates a stream from a callback that can emit values into a queue.
When to use
Use when you need callback-based code to emit stream values by offering to a
Queue, or signal stream completion through the Queue module APIs.
By default it uses an "unbounded" buffer size.
You can customize the buffer size and strategy by passing an object as the
second argument with the bufferSize and strategy fields.
Example (Creating a stream from a callback that can emit values into a queue)
import { Console, Effect, Queue, Stream } from "effect"
const stream = Stream.callback<number>((queue) =>
Effect.sync(() => {
// Emit values to the stream
Queue.offerUnsafe(queue, 1)
Queue.offerUnsafe(queue, 2)
Queue.offerUnsafe(queue, 3)
// Signal completion
Queue.endUnsafe(queue)
})
)
const program = Effect.gen(function*() {
const values = yield* stream.pipe(Stream.runCollect)
yield* Console.log(values)
// [ 1, 2, 3 ]
})
Effect.runPromise(program)
callback = <function (type parameter) A in <A, E = never, R = never>(f: (queue: Queue.Queue<A, E | Cause.Done>) => Effect.Effect<unknown, E, R | Scope.Scope>, options?: {
readonly bufferSize?: number | undefined;
readonly strategy?: "sliding" | "dropping" | "suspend" | undefined;
}): Stream<A, E, Exclude<R, Scope.Scope>>
function (type parameter) E in <A, E = never, R = never>(f: (queue: Queue.Queue<A, E | Cause.Done>) => Effect.Effect<unknown, E, R | Scope.Scope>, options?: {
readonly bufferSize?: number | undefined;
readonly strategy?: "sliding" | "dropping" | "suspend" | undefined;
}): Stream<A, E, Exclude<R, Scope.Scope>>
function (type parameter) R in <A, E = never, R = never>(f: (queue: Queue.Queue<A, E | Cause.Done>) => Effect.Effect<unknown, E, R | Scope.Scope>, options?: {
readonly bufferSize?: number | undefined;
readonly strategy?: "sliding" | "dropping" | "suspend" | undefined;
}): Stream<A, E, Exclude<R, Scope.Scope>>
f: (
queue: Queue.Queue<A, E | Cause.Done>
) => Effect.Effect<unknown, E, R | Scope.Scope>
queue: Queue.Queue<A, E | Cause.Done>(parameter) queue: {
strategy: "suspend" | "dropping" | "sliding";
dispatcher: SchedulerDispatcher;
capacity: number;
messages: MutableList.MutableList<any>;
state: Queue.State<any, any>;
scheduleRunning: boolean;
toString: () => string;
toJSON: () => unknown;
}
import QueueQueue.interface Queue<in out A, in out E = never>A Queue is an asynchronous queue that can be offered to and taken from.
Details
It also supports signaling that it is done or failed.
Example (Offering and taking queue values)
import { Effect, Queue } from "effect"
const program = Effect.gen(function*() {
// Create a bounded queue
const queue = yield* Queue.bounded<string>(10)
// Producer: offer items to the queue
yield* Queue.offer(queue, "hello")
yield* Queue.offerAll(queue, ["world", "!"])
// Consumer: take items from the queue
const item1 = yield* Queue.take(queue)
const item2 = yield* Queue.take(queue)
const item3 = yield* Queue.take(queue)
console.log([item1, item2, item3]) // ["hello", "world", "!"]
})
Companion namespace containing type-level metadata and low-level state types
for Queue.
Queue<function (type parameter) A in <A, E = never, R = never>(f: (queue: Queue.Queue<A, E | Cause.Done>) => Effect.Effect<unknown, E, R | Scope.Scope>, options?: {
readonly bufferSize?: number | undefined;
readonly strategy?: "sliding" | "dropping" | "suspend" | undefined;
}): Stream<A, E, Exclude<R, Scope.Scope>>
function (type parameter) E in <A, E = never, R = never>(f: (queue: Queue.Queue<A, E | Cause.Done>) => Effect.Effect<unknown, E, R | Scope.Scope>, options?: {
readonly bufferSize?: number | undefined;
readonly strategy?: "sliding" | "dropping" | "suspend" | undefined;
}): Stream<A, E, Exclude<R, Scope.Scope>>
import CauseCause.interface Done<A = void>A graceful completion signal for queues and streams.
When to use
Use to model normal producer completion through a stream or queue error
channel.
Details
Done indicates that a producer has finished normally — no more elements
will arrive. It is distinct from an error or interruption; it represents
successful completion. The optional value field can carry a final
leftover payload.
Example (Signaling queue completion)
import { Cause, Effect, Queue } from "effect"
const program = Effect.gen(function*() {
const queue = yield* Queue.bounded<number, Cause.Done>(10)
yield* Queue.offer(queue, 1)
yield* Queue.end(queue)
const result = yield* Effect.flip(Queue.take(queue))
console.log(Cause.isDone(result)) // true
})
Companion namespace for the Done interface.
Creates a Done signal with an optional value.
When to use
Use when you need to construct a low-level pull completion signal directly.
Done>) => import EffectEffect.interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<unknown, function (type parameter) E in <A, E = never, R = never>(f: (queue: Queue.Queue<A, E | Cause.Done>) => Effect.Effect<unknown, E, R | Scope.Scope>, options?: {
readonly bufferSize?: number | undefined;
readonly strategy?: "sliding" | "dropping" | "suspend" | undefined;
}): Stream<A, E, Exclude<R, Scope.Scope>>
function (type parameter) R in <A, E = never, R = never>(f: (queue: Queue.Queue<A, E | Cause.Done>) => Effect.Effect<unknown, E, R | Scope.Scope>, options?: {
readonly bufferSize?: number | undefined;
readonly strategy?: "sliding" | "dropping" | "suspend" | undefined;
}): Stream<A, E, Exclude<R, Scope.Scope>>
import ScopeScope.Scope>,
options: | {
readonly bufferSize?: number | undefined
readonly strategy?:
| "sliding"
| "dropping"
| "suspend"
| undefined
}
| undefined
bufferSize?: number | undefinedbufferSize?: number | undefined
readonly strategy?: | "sliding"
| "dropping"
| "suspend"
| undefined
interface Stream<out A, out E = never, out R = never>A Stream<A, E, R> describes a program that can emit many A values, fail
with E, and require R.
Details
Streams are pull-based with backpressure and emit chunks to amortize effect
evaluation. They support monadic composition and error handling similar to
Effect, adapted for multiple values.
Example (Creating and consuming streams)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
yield* Stream.make(1, 2, 3).pipe(
Stream.map((n) => n * 2),
Stream.runForEach((n) => Console.log(n))
)
})
Effect.runPromise(program)
// Output:
// 2
// 4
// 6
Stream<function (type parameter) A in <A, E = never, R = never>(f: (queue: Queue.Queue<A, E | Cause.Done>) => Effect.Effect<unknown, E, R | Scope.Scope>, options?: {
readonly bufferSize?: number | undefined;
readonly strategy?: "sliding" | "dropping" | "suspend" | undefined;
}): Stream<A, E, Exclude<R, Scope.Scope>>
function (type parameter) E in <A, E = never, R = never>(f: (queue: Queue.Queue<A, E | Cause.Done>) => Effect.Effect<unknown, E, R | Scope.Scope>, options?: {
readonly bufferSize?: number | undefined;
readonly strategy?: "sliding" | "dropping" | "suspend" | undefined;
}): Stream<A, E, Exclude<R, Scope.Scope>>
type Exclude<T, U> = T extends U
? never
: T
Exclude from T those types that are assignable to U
Exclude<function (type parameter) R in <A, E = never, R = never>(f: (queue: Queue.Queue<A, E | Cause.Done>) => Effect.Effect<unknown, E, R | Scope.Scope>, options?: {
readonly bufferSize?: number | undefined;
readonly strategy?: "sliding" | "dropping" | "suspend" | undefined;
}): Stream<A, E, Exclude<R, Scope.Scope>>
import ScopeScope.Scope>> => const fromChannel: <
Arr extends Arr.NonEmptyReadonlyArray<any>,
E,
R
>(
channel: Channel.Channel<
Arr,
E,
void,
unknown,
unknown,
unknown,
R
>
) => Stream<
Arr extends Arr.NonEmptyReadonlyArray<infer A>
? A
: never,
E,
R
>
Creates a stream from a array-emitting Channel.
Example (Creating a stream from an array-emitting channel)
import { Channel, Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
const channel = Channel.succeed([1, 2, 3] as const)
const stream = Stream.fromChannel(channel)
const result = yield* Stream.runCollect(stream)
yield* Console.log(result)
})
// Output: [ 1, 2, 3 ]
fromChannel(import ChannelChannel.const callbackArray: <
A,
E = never,
R = never
>(
f: (
queue: Queue.Queue<A, E | Cause.Done>
) => Effect.Effect<unknown, E, R | Scope.Scope>,
options?: {
readonly bufferSize?: number | undefined
readonly strategy?:
| "sliding"
| "dropping"
| "suspend"
| undefined
}
) => Channel<
Arr.NonEmptyReadonlyArray<A>,
E,
void,
unknown,
unknown,
unknown,
Exclude<R, Scope.Scope>
>
Creates a Channel that interacts with a callback function using a queue, emitting arrays.
Example (Creating array channels from callbacks)
import { Channel, Effect, Queue } from "effect"
const channel = Channel.callbackArray<number>(Effect.fn(function*(queue) {
yield* Queue.offer(queue, 1)
yield* Queue.offer(queue, 2)
}))
// Emits arrays of numbers instead of individual numbers
callbackArray(f: (
queue: Queue.Queue<A, E | Cause.Done>
) => Effect.Effect<unknown, E, R | Scope.Scope>
options: | {
readonly bufferSize?: number | undefined
readonly strategy?:
| "sliding"
| "dropping"
| "suspend"
| undefined
}
| undefined